Peter, J. Paul
Plano, Tex. Business Publication 1982,
Buku Teks
Keller, kotler
Pearson Education, Inc, 2006
Buku Teks
Kotler, Philip
[publisher not identified], [date of publication not identified]
Buku Teks
Kotler, Philip
Prentice-Hall, 2000
Buku Teks
Wilson, Mike
Gower Publishing, 1985
Buku Teks